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  • Other Sources  (39)
  • 1
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    Possible atmospheric lifetimes and chemical reaction mechanisms for selected HCFCs, HFCs, CH3CCl3, and their degradation products against dissolution and/or degradation in seawater and cloudwater (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: For a wide variety of atmospheric species including CO2, HNO3, and SO2, dissolution in seawater or cloudwater followed by hydrolysis or chemical reaction represents a primary pathway for removal from the atmosphere. In order to determine if this mechanism can also remove significant amounts of atmospheric chlorofluorocarbons (HCFC's), fluorocarbons (HFC's), and their degradation products, an investigation was undertaken as part of the Alternative Fluorocarbons Environmental Acceptability Study (AFEAS). In this investigation, the rates at which CHCl2CF3 (HCFC-123), CCl2FCH3 (HCFC-141b), CClF2CH3 (HCFC-142b), CHClF2 (HCFC-22), CHClFCF3 (HCFC-124) CH2FCF3 (HFC-134a) CHF2CH3 (HFC-152a), CHF2CF3 (HFC-125), and CH3CCl3 can be dissolved in the oceans and in cloudwater were estimated from the species' thermodynamic and chemical properties using simple mathematical formulations to simulate the transfer of gases from the atmosphere to the ocean or cloudwater. The ability of cloudwater and rainwater to remove gas phase degradation products of these compounds was also considered as was the aqueous phase chemistry of the degradation products. The results of this investigation are described.
    Keywords: ENVIRONMENT POLLUTION
    Type: NASA, Washington, Scientific Assessment of Stratospheric Ozone: 1989, Volume 2. Appendix: AFEAS Report; p 271-295
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  • 2
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    Lightning - Estimates of the rates of energy dissipation and nitrogen fixation (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The nitrogen needed by plants can normally not be directly obtained from the nitrogen present in molecular form in the atmosphere. The reason for this situation is related to the great energy required to break the N-N bond. Only a few organisms, such as algae and certain bacteria, can 'fix' nitrogen. An abiological process for breaking the N-N bond is provided by lightning. The present investigation is concerned with this possibility. It is found that lightning produces approximately 2.6 x 10 to the 9th kg N per year. There are, however, uncertainties, which are mainly related to the energy of a lightning flash.
    Keywords: GEOPHYSICS
    Type: Reviews of Geophysics and Space Physics (ISSN 0034-6853); 22; 363-372
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  • 3
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    The rainout parameterization in a photochemical model (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Photochemical models of tropospheric trace species typically simulate the effects of wet removal of soluble species from the atmosphere through a first-order rainout parameterization, which is independent of the species solubility and constant in time. In this work a modified first-order rainout parameterization is proposed that is a function of the species' solubility and takes into account the intermittent nature of atmospheric wet removal. In the case of a highly soluble species, such as HNO3, the inclusion of the effects of intermittent rainout in the parameterization leads to averaged rainout lifetimes considerably higher than ones used in most photochemical models. For illustrative purposes this parameterization is applied to a one-dimensional steady state model with parameterized eddy diffusion, although in principle it can be used in more sophisticated multidimensional models. The model results are compared to analagous calculations obtained with a 3-D tracer transport model.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 7872-788
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  • 4
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    The chemistry and transport of methane and carbon monoxide in the troposphere (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The present understanding of the physical and chemical behavior of methane, carbon monoxide and the chemical species involved in the conversion of CH4 to CO in the troposphere is reviewed. Following a brief summary of CO and CH4 emission and reactions in urban areas, attention is given to measurements of the spatial and temporal distributions of CO and CH4 in the rural atmosphere, the contribution of the oceans to atmospheric CO and CH4 concentrations, and interactions of CH4 and CO with soils and vegetation. Estimates of the transport of CH4 and CO from the troposphere to the stratosphere are discussed, and photochemical reactions of the constituents are examined. Two- and three-dimensional models for CH4 and CO transport are presented, and possible future variations in atmospheric abundances of the molecules are considered. Finally, present estimates of the global methane and carbon dioxide budgets are summarized, and it is pointed out that, despite the large contribution of anthropogenic sources, the budgets appear to be in balance.
    Keywords: ENVIRONMENT POLLUTION
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  • 5
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    Iodine - Its possible role in tropospheric photochemistry (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A detailed study of the photochemistry of iodine and its oxides indicates that iodine species may play an important role in the tropospheric photochemical system. Methyl iodide, often observed in the marine troposphere with an average concentration of 5-10 ppt, is photolyzed and thereby produces I atoms. Chemical interactions with O3, HxOy, and NOx cause I to be converted to other inorganic compounds such as IO, HOI, IONO2, and I2. The production of these species and their subsequent recycling back to I can lead to the catalytic removal of tropospheric O3, the enhancement of the NO2/NO ratio, the destruction of HxOy free radicals, and the conversion of HO2 to OH. Ultimately, tropospheric inorganic iodine is removed by heterogeneous processes. Calculations using a numerical model to simulate tropospheric photochemistry indicate that iodine may have a strong impact upon the atmospheric O3-NOx-HxOy system. The magnitude of these effects is dependent upon the value of several uncertain rate constants and the primary source distributions of CH3I and other organic and inorganic iodine compounds.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 85; Dec. 20
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  • 6
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    Potential role of CS2 photooxidation in tropospheric sulfur chemistry (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Absorption cross section measurements and model calculations indicate that CS2 photooxidation may be an important tropospheric sink for the CS2, giving a lifetime on the order of a week or two. If background CS2 levels are 10-20 pptv, then CS2 photooxidation may be an important global source of OCS as well.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters; 8; May 1981
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  • 7
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    Actinometric measurements and theoretical calculations of j/O3/, the rate of photolysis of ozone to O/1D/ (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The paper presents an experimental technique which measures j/O3-O(1-D)/, the rate of solar photolysis of ozone to singlet oxygen atoms. It is shown that a flow actinometer carries dilute O3 in N2O into direct sunlight where the O(1D) formed reacts with N2O to form NO which chemiluminescence detects, with a time resolution of about one minute. Measurements indicate a photolysis rate of 1.2 (+ or - .2) x 10 to the -5/s for a cloudless sky, 45 deg zenith angle, 0.345 cm ozone column and zero albedo. Finally, ground level results compare with theoretical calculations based on the UV actinic flux as a function of ozone column and solar zenith angle.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters; 6; Nov. 197
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  • 8
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    A perturbative treatment of aerosol scattering of infrared radiation (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Calculations of long-wave atmospheric heating and cooling rates using the rate equations of Rodgers and Walshaw (1966) with the Malkmus (1967) random band model are presented. A perturbation scheme is developed for the inclusion of aerosol scattering effects in the numerical calculation. Unlike the flux differencing method for calculating long-wave heating and cooling rates, this scheme allows aerosol effects to be included in a simple manner with only a small additional use of computer time. The calculations indicate good agreement with those of previous investigators and demonstrate the expected equivalence of the flux-differencing method and the flux-divergence equation of Rodgers and Walshaw (1966), even at stratospheric altitudes. It is found that aerosols lead to a net heating in the lower troposphere due to infrared scattering and absorption.
    Keywords: GEOPHYSICS
    Type: Journal of the Atmospheric Sciences; 36; Oct. 197
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  • 9
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    The free radical chemistry of cloud droplets and its impact upon the composition of rain (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Calculations are presented that simulate the free radical chemistries of the gas phase and aqueous phase within a warm cloud during midday. It is demonstrated that in the presence of midday solar fluxes, the heterogeneous scavenging of OH and HO2 from the gas phase by cloud droplets can represent a major source of free radicals to cloud water, provided the accommodation or sticking coefficient for these species impinging upon water droplets is not less than 0.0001. The aqueous-phase of HO2 radicals are found to be converted to H2O2 by aqueous-phase chemical reactions at a rate that suggests that this mechanism could produce a significant fraction of the H2O2 found in cloud droplets. The rapid oxidation of sulfur species dissolved in cloudwater by this free-radical-produced H2O2 as well as by aqueous-phase OH radicals could conceivably have a significant impact upon the chemical composition of rain.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Geophysical Research; 87; June 20
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  • 10
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    The two-dimensional diagnostic model for tropospheric OH - An uncertainty analysis (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Tropospheric OH is believed to play a major role in atmospheric photochemistry, and, via its chemical interactions OH ultimately may affect the climate, stratospheric ozone levels, and the pH of rain. A valuable tool for predicting the global OH abundance as a function of latitude and altitude is the two-dimensional diagnostic model for tropospheric OH. This model can also be applied to budget studies of species which interact with OH, such as CH4, CO, and O3. In addition to laboratory-obtained kinetic data, important variables include the rate constants for several reactions, the rate of heterogeneous removal of soluble species, and the global abundance and spatial variability in H2O, O3, CO, and NOx. The uncertainties in these parameters imply over a factor of 3 variability in the calculated global OH concentration as well as significant uncertainties in the latitudinal and vertical OH distribution.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 86; June 20
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